U.S. patent application number 16/301506 was filed with the patent office on 2019-10-10 for neural device of performing conditioned response and method of driving the same.
This patent application is currently assigned to Industry-University Cooperation Foundation Hanyang University. The applicant listed for this patent is Industry-University Cooperation Foundation Hanyang University. Invention is credited to Hwan Young CHOI, Tae Whan KIM, Dae Uk LEE, Chaoxing WU.
Application Number | 20190311250 16/301506 |
Document ID | / |
Family ID | 61245125 |
Filed Date | 2019-10-10 |
United States Patent
Application |
20190311250 |
Kind Code |
A1 |
KIM; Tae Whan ; et
al. |
October 10, 2019 |
NEURAL DEVICE OF PERFORMING CONDITIONED RESPONSE AND METHOD OF
DRIVING THE SAME
Abstract
A neural device to which a conditioned response function is
imparted and a driving method thereof are disclosed. Quantum dots
and a polymer insulating layer are formed between upper and lower
electrodes. Conductive filaments are formed at interfaces between
the quantum dots and the polymer insulating layer. When a positive
pulse, which is an unconditioned stimulus signal, is applied, the
conductive filaments are formed, and a low resistance state is
implemented. As the number of applications of a negative pulse,
which is a conditioned stimulus signal, increases, the neural
device is switched from a high resistance state to the low
resistance state. Through this, the neural device having learning
ability for the conditioned stimulus signal may be implemented and
driven.
Inventors: |
KIM; Tae Whan; (Seoul,
KR) ; WU; Chaoxing; (Seoul, KR) ; LEE; Dae
Uk; (Goyang-si, KR) ; CHOI; Hwan Young;
(Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Industry-University Cooperation Foundation Hanyang
University |
Seoul |
|
KR |
|
|
Assignee: |
Industry-University Cooperation
Foundation Hanyang University
Seoul
KR
|
Family ID: |
61245125 |
Appl. No.: |
16/301506 |
Filed: |
August 24, 2017 |
PCT Filed: |
August 24, 2017 |
PCT NO: |
PCT/KR2017/009245 |
371 Date: |
November 14, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06N 3/0635 20130101;
G06N 3/063 20130101; G06N 3/08 20130101 |
International
Class: |
G06N 3/063 20060101
G06N003/063; G06N 3/08 20060101 G06N003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2016 |
KR |
10-2016-0107921 |
Claims
1. A neural device comprising: a lower electrode; quantum dots
formed on the lower electrode; a polymer insulating layer filling a
separation space between the quantum dots; and an upper electrode
formed on the quantum dots and the polymer insulating layer, and
contacted with the quantum dots, wherein the upper electrode
supplies metal cations to an interface between the quantum dots and
the polymer insulating layer to form conductive filaments by
reduction of the metal cations.
2. The device of claim 1, wherein the lower electrode includes a
material such as Au, Pt, Cr, Ni, Al, Cu, Ag, Au, Ni, Zn, Cd, Pd Ti,
AlZnO, or ITO.
3. The device of claim 1, wherein the quantum dot includes
Al.sub.2O.sub.3, and a diameter of the quantum dot is 5 nm to 10
nm.
4. The device of claim 1, wherein the polymer insulating layer
includes polyimide.
5. The device of claim 1, wherein the upper electrode includes Cu,
Ag, Au, Ni, Zn, Cd, Pd, or an alloy thereof.
6. (canceled)
7. A method of driving a neural device having quantum dots and a
polymer insulating layer between an upper electrode and a lower
electrode, the method comprising: applying a positive voltage
difference between the upper electrode and the lower electrode to
form conductive filaments by supplying metal cations from the upper
electrode in contact with the quantum dots to an interface between
the quantum dots and the polymer insulating layer, thereby allowing
the neural device to enter a low resistance state; applying a
negative voltage difference between the upper electrode and the
lower electrode to remove the conductive filaments adjacent to the
upper electrode by removing the metal cations supplied to the
interface between the quantum dots and the polymer insulating
layer; and alternately applying the positive voltage difference and
the negative voltage difference between the upper electrode and the
lower electrode to accumulate the removed conductive filaments
adjacent to the upper electrode.
8. (canceled)
9. (canceled)
10. The method of claim 7, wherein the positive voltage difference
is used as an unconditioned stimulus, and the negative voltage
difference is used as a conditioned stimulus.
11. The method of claim 10, wherein as the number of repeated
applications of the unconditioned stimulus and the conditioned
stimulus increases, the neural device enters the low resistance
state which is the same as the unconditioned stimulus.
Description
TECHNICAL FIELD
[0001] The present invention relates to a neural device and a
driving method thereof, and more particularly, to a neural device
capable of responding to repeated conditioned signals and a driving
method thereof.
BACKGROUND ART
[0002] Recently, neural network devices which are being studied for
use in artificial intelligence or the like are devices which
imitate a neural transmission system of a human body. The neural
transmission system includes neurons and synapses, and when a
stimulus exceeding a certain range is input, the neurons perform an
operation which produces an output corresponding to the stimulus,
and the synapses perform an operation of transmitting signals to
other neurons with respect to the repeated output of the
neurons
[0003] Thus, when a stimulus exceeding a certain range is applied
or when a stimulus exceeding a certain number is input, a neural
device imitating neurons generates an output corresponding to the
stimulus. Further, a neural device imitating synapses has a
characteristic in which its impedance is changed due to a
continuously applied stimulus.
[0004] Korean Patent Application Publication No. 2016-0056816
discloses neuromorphic devices with an excitatory or inhibitory
function. Which discloses a synapse imitating device having a
structure in which two nMOSs are connected in series, and in which
a program voltage or the like is applied to two lower electrodes to
change a threshold voltage of each channel. In particular, since
the excitatory or inhibitory function may be defined by a bias
applied to an upper electrode, the excitatory or inhibitory
function is implemented according to the bias condition applied to
the upper electrode because it has a series connection structure.
However, it is expected that the consequent output current may not
be largely distinguished.
[0005] Further, Korean Patent Registration No. 1537433 discloses a
memristor device. The memristor device includes a resistance random
access memory and a Schottky diode, which are arranged to be
mutually parallel to selectively operate as a memory or diode.
[0006] However, the above-mentioned patents may not be implemented
to conform to the operating characteristics of neural devices, are
not uniform in processing or response of applied signals due to a
complicated structure thereof, and may cause variations in
characteristic values. Further, manufacturing costs may be
increased due to features including a plurality of functions.
[0007] Accordingly, the appearance of a technique for implementing
a neural device with a simpler structure and operating the neural
device is still required.
DISCLOSURE
Technical Problem
[0008] The present invention is directed to providing a neural
device having a learning function with respect to a conditioned
stimulus.
[0009] The present invention is also directed to providing a method
of driving the neural device having learning function with respect
to a conditioned stimulus.
Technical Solution
[0010] One aspect of the present invention provides a neural device
including a lower electrode; quantum dots formed on the lower
electrode; a polymer insulating layer filling a separation space
between the quantum dots; and an upper electrode formed on the
quantum dots or the polymer insulating layer.
[0011] Another aspect of the present invention provides a method of
driving a neural device having quantum dots and a polymer
insulating layer between an upper electrode and a lower electrode,
including: applying a positive voltage difference between the upper
electrode and the lower electrode to form conductive filaments at
an interface between the quantum dots and the polymer insulating
layer, thereby allowing the neural device to enter a low resistance
state; applying a negative voltage difference between the upper
electrode and the lower electrode to remove the conductive
filaments adjacent to the upper electrode; and alternately applying
the positive voltage difference and the negative voltage difference
between the upper electrode and the lower electrode to accumulate
the removed conductive filaments adjacent to the upper
electrode.
Advantageous Effects
[0012] According to the present invention described above, a
positive pulse corresponding to an unconditioned stimulus and a
negative pulse corresponding to a conditioned stimulus are
repeatedly applied. In an early stage, when the positive pulse,
which is an unconditioned stimulus signal, is applied, the low
resistance state is maintained, and when the negative pulse, which
is a conditioned stimulus signal, is applied, the high resistance
state is maintained. When the conditioned stimulus signal is
repeatedly applied, the neural device learns the signal and
switches to the low resistance state which is the same state as
when the unconditioned stimulus signal is applied.
[0013] Such a method enables the present invention to be utilized
as a neuron device, and the neuron device may be realized with a
simpler structure.
DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a cross-sectional view illustrating a neural
device according to an exemplary embodiment of the present
invention.
[0015] FIGS. 2 to 6 are cross-sectional views illustrating an
operation of the neural device of FIG. 1 according to the exemplary
embodiment of the present invention.
[0016] FIGS. 7 to 9 are cross-sectional views for describing a
method of manufacturing the neural device of FIG. 1 according to
the exemplary embodiment of the present invention.
[0017] FIG. 10 is a graph illustrating response characteristics for
describing an operation of a neural device manufactured according
to a manufacturing example of the present invention.
MODES OF THE INVENTION
[0018] While the present invention is susceptible to various
modifications and alternative forms, specific embodiments thereof
are shown by way of example in the drawings and will herein be
described in detail in the text. It should be understood, however,
that there is no intent to limit the present invention to the
particular forms disclosed, but on the contrary, the present
invention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the present
invention. Similar reference numerals are used for similar elements
in describing each drawing.
[0019] Unless otherwise defined, all terms used herein, including
technical and scientific terms, have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined here.
[0020] Hereinafter, exemplary embodiments of the present invention
will be described more fully with reference to the accompanying
drawings.
Embodiment
[0021] FIG. 1 is a cross-sectional view illustrating a neural
device according to an exemplary embodiment of the present
invention.
[0022] Referring to FIG. 1, a neural device according to the
present exemplary embodiment includes a lower electrode 100,
quantum dots 120, a polymer insulating layer 140, and an upper
electrode 160.
[0023] The lower electrode 100 may be formed of a conductive metal
or a conductive oxide, for example, indium tin oxide (ITO) or the
like. The lower electrode may include a material such as Au, Pt,
Cr, Ni, Al, Cu, Ag, Au, Ni, Zn, Cd, Pd Ti, AlZnO, or ITO. A current
flowing through the lower electrode 100 forms an output signal.
[0024] The quantum dots 120 are formed on the lower electrode 100,
and preferably, a quantum dot structure of Al.sub.2O.sub.3 is
formed The quantum dots 120 may be formed by forming an Al layer of
a thin film on a lower electrode 100 and heat-treating the formed
Al layer in an oxygen atmosphere to obtain a regularly arranged
Al.sub.2O.sub.3 structure.
[0025] Further, the polymer insulating layer 140 is formed in a
separation space between the quantum dots 120. The polymer
insulating layer 140 is formed on side parts or upper parts of the
quantum dots 120 and may be formed on exposed surface of the lower
electrode 100 on which the quantum dots 120 are not formed and thus
surfaces thereof are exposed. Further, filaments of metal atoms are
formed or disappeared at interfaces between the quantum dots 120
and the polymer insulating layer 140. That is, the interfaces
between the quantum dots 120 and the polymer insulating layer 140
act as channels in which the filaments formed of the metal atoms
are formed. The polymer insulating layer 140 may include
polyimide.
[0026] The upper electrode 160 is formed on the quantum dots 120 or
the polymer insulating layer 140. The upper electrode 160 may be
formed of metal materials and is selected from materials capable of
supplying the metal atoms to the interfaces of the polymer
insulating layer 140. For example, the upper electrode 160 may
include Cu, Ag, Au, Ni, Zn, Cd, Pd, or an alloy thereof.
[0027] Particularly, a portion of the quantum dots 120 may be
formed in contact with the upper electrode 160. Thus, the
interfaces between the quantum dots 120 and the polymer insulating
layer 140 are formed between the upper electrode 160 and the lower
electrode 100, and a resistance thereof may be adjusted through the
formation and disappearance of the conductive filaments formed at
the interfaces.
[0028] When a positive voltage is applied between the upper
electrode and the lower electrode, metal cations are supplied from
the upper electrode to the interfaces between the quantum dots and
the polymer insulating layer. The supplied metal cations are
reduced by electrons supplied from the lower electrode to form the
conductive filaments of metal particles. Further, when a negative
voltage is applied between the upper electrode and the lower
electrode, the conductive filaments are oxidized to the metal
cations, and the formed metal cations move to the upper electrode
so that conductive channels are disappeared.
[0029] FIGS. 2 to 6 are cross-sectional views illustrating an
operation of the neural device of FIG. 1 according to the exemplary
embodiment of the present invention.
[0030] In FIGS. 2 to 6, the lower electrode 100 is formed of ITO,
the quantum dots 120 are formed of Al.sub.2O.sub.3, the polymer
insulating layer 140 is formed of polyimide, and the upper
electrode 160 is formed of Ag.
[0031] Referring to FIG. 2, the positive voltage is applied to the
upper electrode 160, and the negative voltage or a ground voltage
is applied to the lower electrode 100. That is, a positive voltage
difference V is applied between the upper electrode 160 and the
lower electrode 100. Ag of the upper electrode 160 is ionized to
Ag.sup.+ by the positive voltage applied to the upper electrode
160. That is, an oxidation reaction of Ag occurs in the upper
electrode 160 due to the applied positive voltage. Ag cations
generated in the upper electrode 160 move to the lower electrode
due to the negative voltage or the ground voltage applied to the
lower electrode 100.
[0032] That is, the Ag cations move to the lower electrode 100 due
to a positive potential difference applied between the upper
electrode 160 and the lower electrode 100. The Ag cations move
through an interface 130 between the quantum dot 120 and the
polymer insulating layer 140. However, since the quantum dots 120
have an oxide composition, movement of the metal ions into the
quantum dot is not easy. Further, it is practically impossible for
the metal ions to move into the polymer insulating layer 140 due to
an interlinked and bonded polymer chain structure. However, since
the interface 130 between the quantum dot 120 and the polymer
insulating layer 140 is in a state in which only weak coupling or
physical bonding is performed, the interface 130 may act as a
movement channel for the metal ions.
[0033] The Ag cations move through the interface 130 between the
quantum dot 120 and the polymer insulating layer 140 due to the
negative voltage or the like applied from the lower electrode 100
and move to the lower electrode 100. In the lower electrode 100,
the Ag cations are reduced to be an Ag metal. That is, Ag metal
atoms from the lower electrode 100 are accumulated at the interface
130 between the quantum dot 120 and the polymer insulating layer
140.
[0034] Referring to FIG. 3, the Ag metal atoms are accumulated at
the interface 130 between the quantum dot 120 and the polymer
insulating layer 140 to form filaments of the Ag metal, which are
the conductive channels from the lower electrode 100 to the upper
electrode 160. Thus, a phenomenon in which the resistance between
the upper electrode 160 and the lower electrode 100 is reduced
occurs.
[0035] Referring to FIG. 4, the negative voltage or the ground
voltage is applied to the upper electrode 160, and the positive
voltage is applied to the lower electrode 100. That is, a negative
voltage difference is generated between the upper electrode 160 and
the lower electrode 100, and the Ag metal atoms forming the
conductive filaments disappear from a region close to the upper
electrode 160. That is, the Ag metal atoms are oxidized to cations
through the interface 130 between the quantum dot 120 and the
polymer insulating layer 140 and move to the upper electrode
160.
[0036] Accordingly, a portion of the conductive filaments
connecting between the upper electrode 160 and the lower electrode
100 disappears so that a high resistance state is maintained
between the two electrodes.
[0037] However, the Ag metal atoms at the interface adjacent to the
lower electrode 100 remain and form a portion of the conductive
filaments due to an insufficient pulse width of the negative
voltage difference applied between the two electrodes.
[0038] Referring to FIG. 5, the positive voltage difference is
applied between both electrodes again. That is, the upper electrode
160 has a high voltage, and the lower electrode 100 has a low
voltage. The conductive filaments as illustrated in FIG. 3 are
formed at the interface 130 between the quantum dot 120 and the
polymer insulating layer 140 due to the applied voltage
difference.
[0039] However, since the conductive filaments in FIG. 5 are formed
on the basis of the remaining conductive filaments in FIG. 4, the
number of Ag metal atoms forming the conductive filaments increases
and thus the conductive filaments having a higher density are
formed.
[0040] Subsequently, referring to FIG. 6, the positive voltage is
applied to the lower electrode 100, and the negative voltage or the
ground voltage is applied to the upper electrode 160. That is, the
negative voltage difference is applied between the upper electrode
160 and the lower electrode 100. When the negative voltage
difference is applied, the Ag metal atoms of the conductive
filaments are oxidized, and Ag cations move to the upper electrode
160. However, since the Ag metal atoms forming the conductive
filaments maintain a high density at the interface between the
quantum dot and the polymer insulating layer, the conductive
filaments are maintained for a certain period in which the negative
voltage difference is applied. Thus, the neural device maintains a
low resistance state even when a negative voltage bias is
applied.
[0041] In the above-described mechanisms of FIGS. 2 to 6, when the
positive voltage difference is applied between the upper electrode
160 and the lower electrode 100, the conductive filaments are
formed, and when the negative voltage difference is applied, the
conductive filaments disappear. However, metal atoms of the
conductive filaments are accumulated at the interface between the
quantum dot 120 and the polymer insulating layer 140 while the
positive voltage difference and the negative voltage difference are
alternately and repeatedly formed. Accordingly, when a certain
number of times pass, the low resistance state is maintained
between the upper electrode 160 and the lower electrode 100 even
when the negative voltage difference is applied.
[0042] FIGS. 7 to 9 are cross-sectional views for describing a
method of manufacturing the neural device of FIG. 1 according to
the exemplary embodiment of the present invention.
[0043] Referring to FIG. 7, a metal thin film 110 is formed on the
lower electrode 100. The lower electrode 100 may include a material
such as Au, Pt, Cr, Ni, Al, Cu, Ag, Au, Ni, Zn, Cd, Pd Ti, AlZnO,
or ITO.
[0044] Further, the metal thin film 110 may be formed of Al. For
example, an Al film of 5 nm may be formed on the lower electrode
100 by thermal evaporation.
[0045] Referring to FIG. 8, the metal thin film 110 is formed as
the quantum dots 120 on the lower electrode 100. For example, when
the Al metal thin film formed on the lower electrode 100 is
subjected to a heat treatment process at 300.degree. C. to
400.degree. C. for 0.5 hours to 2 hours in an oxygen atmosphere,
the metal thin film 110 is formed as the quantum dots 120 of
Al.sub.2O.sub.3. A size of the quantum dot 120 may be set to 5 nm
to 10 nm. That is, a diameter of the quantum dot 120 may be set to
5 nm to 10 nm. When the diameter of the quantum dots 120 is less
than 5 nm, it is substantially difficult to form the quantum dots
120 through the heat treatment process, and when the diameter of
the quantum dots 120 exceeds 10 nm, a heat treatment temperature
for forming the quantum dots 120 is increased and a heat treatment
time is increased, thereby decreasing a productivity. When the heat
treatment temperature is less than 300.degree. C., it is difficult
to obtain sufficient melting of the Al metal thin film, and when
the heat treatment temperature exceeds 400.degree. C., the Al metal
thin film is excessively melted and thus the quantum dots 120 of
the desired size may not be formed.
[0046] When the Al metal thin film is subjected to a heat treatment
process in the oxygen atmosphere, the Al metal thin film is
partially melted or combined with oxygen to form Al.sub.2O.sub.3.
Further, the formed Al.sub.2O.sub.3 fine particles act as nuclei
for growth so that a phenomenon, in which Al.sub.2O.sub.3 formed
thereafter is aggregated to the already formed Al.sub.2O.sub.3,
occurs. Through this, the regularly arranged quantum dots of
Al.sub.2O.sub.3 may be obtained. Further, the Al metal thin film is
formed as the quantum dots 120 of Al.sub.2O.sub.3, and regions of
the lower electrode 100 on which the quantum dots are not formed
are exposed due to the aggregation phenomenon.
[0047] Referring to FIG. 9, the separation space between the
quantum dots 120 is filled with the polymer insulating layer 140.
The polymer insulating layer 140 may be formed through a coating
process using a polyimide precursor. A solvent used as the
polyimide precursor to be used is N-methyl-2-pyrrolidone, to which
polyamic acid of p-phenylene biphenyltetracarboximide (BPDA-PDA) is
dissolved. For example, the structure of FIG. 8 is spin-coated with
the polyimide precursor and followed by heat treatment to form the
polymer insulating layer 140.
[0048] Then, the upper electrode 160 is formed on the polymer
insulating layer 140. The upper electrode 160 may include Cu, Ag,
Au, Ni, Zn, Cd, Pd, or an alloy thereof. In particular, the upper
electrode 160 supplies the metal ions to form the conductive
filaments.
[0049] The upper electrode 160 may be formed through a conventional
thermal evaporation method.
[0050] Further, the upper electrode 160 may be formed in contact
with the polymer insulating layer 140 and a portion of top surfaces
of the quantum dots 120.
Manufacturing Example
[0051] FIG. 10 is a graph illustrating response characteristics for
describing an operation of a neural device manufactured according
to a manufacturing example of the present invention.
[0052] Referring to FIG. 10, ITO is used as a lower electrode, and
Ag is used as an upper electrode. Further, quantum dots are formed
of Al.sub.2O.sub.3, and polyimide is used as a polymer insulating
layer. A thermally evaporated Al metal thin film is heat-treated at
350.degree. C. for 1 hour in an oxygen atmosphere to form the
quantum dots. The polyimide precursor used is
N-methyl-2-pyrrolidone to which polyamic acid of p-phenylene
biphenyltetracarboximide (BPDA-PDA) is dissolved and is spin-coated
at 7800 rpm.
[0053] A pulse signal is alternately applied between the upper
electrode and the lower electrode of the neural device manufactured
through the above-described process. For example, a pulse of +5 V
and a pulse of -5 V are alternately applied between the upper
electrode and the lower electrode, and a current flowing through
the lower electrode is measured. A current flowing out from the
lower electrode is set to (+), and a current flowing into the lower
electrode is defined as (-), each of which is defined to have a
pulse width of 10 nsec.
[0054] Referring to FIG. 10, when the pulse of +5 V is applied, the
current measured at the lower electrode increases due to the
formation of conductive filaments, and through this, it can be seen
that the neural device is in a low resistance state. Further, at an
early stage of the application of the pulse of -5 V, the current
measured at the lower electrode is very small due to the
disappearance of the conductive filaments.
[0055] When the pulse of +5V and the pulse of -5V are repeatedly
applied, metal atoms of the conductive filaments are accumulated at
the interface between the quantum dots and the polymer insulating
layer. Accordingly, a phenomenon in which a negative current value
increases even in a state in which the pulse of -5 V is applied
occurs. Thus, finally, it can be seen that the conductive filaments
do not disappear and maintain the low resistance state even in a
state in which the negative pulse is applied.
[0056] That is, when a voltage of +5 V and a voltage of -5 V are
repeatedly applied, an output signal is changed such that a
negative output current level is gradually saturated to a constant
value according to the number of applied pulses, and a positive
output current level is maintained in a stable high current
state.
[0057] The above-described operation may be construed as a passage
of neurons with respect to an input signal including an
unconditioned stimulus and a conditioned stimulus. That is, one
pulse having a magnitude of 5V may be defined as the unconditioned
stimulus, and one pulse having a magnitude of -5V may be defined as
the conditioned stimulus. An output current for each pulse is
represented as a conditioned response and an unconditioned
response.
[0058] For example, Pavlov's experiments with dogs may be used to
understand neural learning behavior of the neural device. In the
early stages, only ringing of a bell may not make the dog salivate.
However, when the dog is given a training course that repeats the
act of feeding the dog while ringing the bell, Pavlov's dog
develops an ability to associate with the bell and the food, and as
a result, the dog secretes saliva only with the ringing of the
bell.
[0059] In the present invention, the pulse of 5V is the
unconditioned stimulus (a stimulus such as food), which is applied
to the neural device, and the pulse of -5V may be set as the
conditioned stimulus (a stimulus such as a bell). When the
conditioned stimulus is continuously applied to increase the number
of instances of training, which is a training process, a current of
the same level as the output current which appears in the
unconditioned stimulus may be obtained. Accordingly, it can be seen
that the neural device learns the input stimulus signal and forms
an effective relationship between the conditioned stimulus and the
unconditioned stimulus.
[0060] According to the present invention described above, a
positive pulse corresponding to the unconditioned stimulus and a
negative pulse corresponding to the conditioned stimulus are
repeatedly applied. In an early stage, when the positive pulse,
which is an unconditioned stimulus signal, is applied, the low
resistance state is maintained, and when the negative pulse, which
is a conditioned stimulus signal, is applied, the high resistance
state is maintained. When the conditioned stimulus signal is
repeatedly applied, the neural device learns the signal and
switches to the low resistance state which is the same state as
when the unconditioned stimulus signal is applied.
[0061] Such a method enables the present invention to be utilized
as a neuron device, and the neuron device may be realized with a
simpler structure.
* * * * *